Exam 3 Flashcards
How does multicellular organisms begin life?
Multicellular organisms begin life as a single cell life
Asexual reproduction
Doesn’t require sperm and egg
Require in sexual reproduction
Why is cellular reproduction necessary?
production of both new cells and new organisms
Cell division
parent cell contents divides into two daughter cells
Cell Growth
cell duplicates its contents (including DNA and organelles)
Chromation
DNA and associated proteins have the appearance of thin threads
DNA
periodically wound around histones to form nucleosomes
How many chromosomes does humans have
46 Chromosomes
What is sister Chromatids
Duplicated chromosomes are composed of sister chromatids joined at the centromere
What does each sister chromatid have
Identical DNA
Prophase
chromosomes are visible under microscope in condensed pairs
Metaphase
chromosomes line up along equatorial plate
Anaphase
chromosomes are pulled to opposite poles of cells
Telophase and Cytokinesis
two distinct cells are visible under the microscope
what happens mitosis begins?
DNA is replicated
what does each chromosomes consists of?
two sister chromatids attached at a centromere
Mitosis differs in plants and animals
Plant- have centrosomes but lacks centrioles
Animals- each centromoses has two centrioles and an sister (array of microtubules)
Cell plate
newly formed plasma membrane
G1 check point
cell committed to divide after this point
can enter G0 if checkpoint not passed
G2 checkpoint
Verifies that DNA replicated
DNA damage repaired
Mitotic stage checkpoint
Between metaphase and anaphase
all chromosomes must be attached to spindle to pass
Signal
a molecule that stimulates or inhibits an events
External signals
comes from outside the cell
internal signals
come from inside the cell
Kinases
removes a phosphate from ATP and add it to other molecules
Cyclins
internal signals present only during certain stages of the cell cycle
Epidermal growth factor
(EGF) stimulates skin near an injury to finish cell cycle and repair injury
Hormone estrogen
stimulates lining of the uterus to divide and prepare for egg implantation
Contact inhibition
cells stop dividing when they touch
Proto-oncogenes
code for proteins that promote the cell cycle and inhibits apoptosis. They are often likened to the gas pedal of a car because they accelerate the cell cycle
Tumor suppressor genes
code for proteins that inhibits the cell and promote apoptosis
Carcinogenesis
development of cancer
Benign
contained within a capsule
Malignant
invasion and may spread
Two major functions of meiosis
reducing chromosome number
shuffling chromosomes in the cell to produce genetically different gametes
Homologous chromosomes
members of a pair of chromosomes
have the same size, shape, and construction
contain the same genes for the same traits
Alleles
alternate forms of a gene
Msiosis I
homologous pairs line up during synapsis resulting in tetrad
homologous chromosomess of each pair then separate
Meiosis II
No duplication chromosomes
chromosomes are dyads- composed of two sisters chromatids
sister chromatids are separated
two daughter nuclei separate
tetrad
consists of two chromosomes, with each chromosome containing two chromatids,
for a total of 4 chromatids
Meiosis
two consecutive nuclear divisions; mitosis- only one nuclear divisions
What occurs prophase I of meiosis
synapsis
What happens during metaphase I
tetrad align at the spindle equator, with homologous chromosomes facing opposite spindle pole and paired chromosomes have a total of four chromatids each
What does not happen in anaphase I
sister chromatids do not separate
Trisomy
three copies of a chromosomes
Monosomy
single copy of a chromosome
Turner syndrome
absence of second sex chromosomes
female
Klinefelter syndrome
extra X inactivated as Barr body
Male
Gregor Mendel
Austrian monk
worked with garden pea plants in 1890s
One- trait inheritance
original parents called P generation
Punnett square
shows all possible combinations of egg and sperm offspring may inherit
testcross
used to determine whether or not an individual with the dominant trait has two dominant factors for a particular trait
Alleles
alternative forms of a gene
occurs on homologous chromosomes at a particular location called the gene locus
Genotype
alleles the individual receives at fertilization
Homozygous
two identical alleles
homozygous dominant
homozygous recessive
Heterozygous
two different alleles
Phenotype
physical appereance of the individual
mostly determined by genotype
Mendel’s First law of inheritance
Law of segregation
Law of Segregation
Each individual has two factors for each trait
The factors segregate (separate) during the formation of the gametes
Each gamete contains only one factor from each pair of factors
Fertilization gives each new individual two factors for each trait
Alleles
Dominant allele masks the expression of the recessive allele
For the most part, an individual’s traits are determined by the alleles inherited.
Alleles occur on homologous chromosomes at a particular location called the gene locus
Mendel’s Second Law of Heredity
Law of independent assortment
Law of independent assortment
Each pair of factors segregates (assorts) independently of the other pairs.
All possible combinations of factors can occur in the gametes.
Punnett squares assumes
each gamete contains one allele for each trait
Pedigree
Chart of a family’s history in regard to a particular genetic trait
Males are squares
Females are circles
Shading represents individuals expressing disorder
Horizontal line between circle and square is a union
Vertical line down represents children of that union
Methemoglobinemia
lack enzyme to convert methemoglobin back to hemoglobin
Cystic fibrosis
autosomal recessive disorder
Most common lethal genetic disorder among Caucasians in U.S.
Chloride ion channel defect causes abnormally thick mucus
Polygenic inheritance
Trait is governed by two or more sets of alleles
Each dominant allele has a quantitative effect on phenotype and effects are additive
Result in continuous variation—bell-shaped curve
Multifactorial traits
polygenic traits subject to environmental effects
Cleft lip, diabetes, schizophrenia, allergies, cancer
Due to combined action of many genes plus environmental influences
Pleiotropy
Single genes have more than one effect
Gene linkage
two traits on same chromosome
Linked alleles stay together
heterozygote forms only two types of gametes, produces offspring only with two phenotypes
what is the first stage of Mitosis
Prophase
Prophase
chromosomes are visible under microscope in condensed pairs
what is the second stage of Mitosis
Metaphase
Metaphase
chromosomes line up along equatorial plate (middle)
what is the third stage of Mitosis
Anaphase
Anaphase
chromosomes are pulled to opposite poles of cell (apart)
What is the final stage of Mitosis
Telophase
Telophase
two distinct cells are visible under the microscopes
What is Mitosis usually followed by
cytokinesis
How do plant and animal cells differ from each other
Plant- have centrosomes but lack centrioles
Animal- each centrosomes has two centrioles and an aster (array of microtubules)
